Hair analyiss critical analysis PDF

Preview

Summary

Download Hair analyiss critical analysis PDF

Description

Hair comparisons have been used as an investigative and evidentiary tool in criminal cases for over a century (Rowe, 2001) and remains relevant today. The technique, however, has not been without significant scrutiny and critique, particularly regarding its use as expert testimony in cases of wrongful conviction (Cole & Duster, 2016). This essay will firstly discuss the strengths of microscopic hair analysis, including its availability and low resource requirement and investigative capabilities. Then next, will discuss its’ limitations, including issues with the examiner and their testimony, lack of standards, and the inconsistent nature of hair. Finally, it will reflect on the future of microscopic hair analysis and its use as expert testimony to reduce future wrongful convictions.

Hairs are one of the most common, and may be the only, form of evidence located at a crime scene (Oien, 2009). Following a hair being recovered, attempts are made to identify from whom the hair could have originated. This is done by collecting hair samples from persons of interest and comparing these known origin hairs to those currently unknown; as hairs are expected to share most, if not all, characteristics if they originated from the same individual and body location (Cole & Duster, 2016). Using a ‘transmitted-light comparison microscope’, the two hair samples are scrutinized, and their features compared, to identify whether they are microscopically similar (Rowe, 2001). Whist it is not possible to definitively identify any individual through microscopic

hair analysis alone, the more distinctive and uncommon in the relevant population observed characteristic ‘matches’ are, the greater the chance suspect is the original source (McQuiston-Surrett & Saks, 2009).

The major strengths of hair analysis are that hair evidence is abundant, is highly transferrable and is generally accepted to be distinct enough to narrow a ‘potential source’ pool (National Academy of Sciences [NAS], 2009). It is readily available as most humans have at least some hair, it is naturally shed, is visible to the naked eye and can provide some immediately useful information regarding the circumstances of the crime, as well as potentially identifying class features such as the natural or altered colour, length, and style (Taupin, 2004). Hair is also relatively difficult to destroy and may withstand environments and time better than some other evidence (Taupin, 2004). Importantly, during initial investigative stages, relevant information and evidence must be identified and appropriately collected. Thus, to be examined, hairs must be identified as having some investigative value. Robertson (2017) notes that the location in which a hair is found may prove to be equally important as identifying its origin.

Another strength of microscopic hair analysis is that there are minimal resources and facility requirements to perform the tests. As such, hair evidence can be examined in laboratories which cannot perform DNA tests on the hairs (Taupin, 2004). Further, the

test is non-destructive to the sample which consequently may be retested later if required (Taupin, 2004).

The major limitations of microscopic hair analysis are discussed in the report by the National Academy of Sciences (NAS) (2009), including: the subjectivity and reliance on the examiner’s ‘proficiency and practical experience’, the use of misleading and ambiguous terminology and overstatements, the lack of ‘scientifically accepted statistics’ regarding hair characteristic distribution within the population, and a lack of standardisation concerning what constitutes a match. Another limitation of hair analysis is that its error-rate is currently seemingly unquantifiable. In the 1970’s, Gaudette (as cited in Giannelli, 2010), published several articles later largely discredited, attempting to estimate the likelihood of a ‘false match’, or incorrect association, in hair analysis. Gaudette’s data estimated the probability of a ‘false match’ as “1 in 4,500” and “1 in 800” for head and pubic hairs respectively (Gaudette, as cited in Gianelli, 2010).

As the determination of similarity is made by the examiner based upon their practical experience and knowledge and is highly subjective (NAS, 2009), increasing objectivity is one goal to increase accuracy and reliability. One of the major characteristics of hair observable is colour, which is highly subjective. Furthermore, an examiner’s descriptions of characteristics, including colour, may vary over time (Taupin, 2004). Mills, Bonetti, Brettell and Quarino, (2018) express that the human eye is not

capable of differentiating the complex colours and subtle differences exhibited in hair and that technological advancements may now allow for ‘digital imaging software’ to assist analysis. The more objective and sensitive colour assessment produced by the computer software in the study by Mills et al. hints at the future possibilities and development of further technological assistance with microscopic hair analysis tests, and the potential for testing examiner accuracy.

These subjective assessments may be further complicated by the prevalence of ‘featureless’, sparsely pigmented, and artificially coloured hair (Smith & Linch, 1999). As microscopic hair analysis relies on the identification and correlation of observable characteristics, hairs with limited features are more challenging to compare against each other.

Expert testimonies in multiple cases, as expressed by Giannelli (2010), have included severely overstated claims, leading to wrongful convictions. In some courts, microscopic hair analysis does not strictly meet the criteria for admissibility, such as under the Daubert decision, where the technique’s potential error-rate must be known, (Rowe, 2001). In the several instances in which courts have permitted this overstated expert hair testimony, as Giannelli (2010) describes, the capability of microscopic hair analysis should have been well understood by both the expert and prosecution. Although, through its’ admittance, it is strongly indicated that there was a lack of understanding of

the evidence. The overstatement trend noted by Giannelli (2010) has been suggested by Cole and Duster (2016) to be related to training and a lack of understanding of hair analysis evidence both in the scientific and non-scientific community. This is also supported by McQuinston-Surrett and Saks (2009), whom express that the wording used in expert hair testimonies may have some impact on juror and judge understanding and their given weight of evidence on guilt.

The statistical understanding of microscopic hair analysis accuracy and reliability is currently limited and incomplete (NAS, 2009). In one study attempting to determine false-positive associations by Wickenheiser and Hepworth (as cited in Rowe, 2001), both examiners correctly and independently matched six and seven hairs respectively, with zero incorrect matches. Of the matches made by Wickenheiser and Hepworth, only one was shared, as they each classified the remaining five and six matches differently, despite the given categorisation. These results strongly suggest that individual training and experience are highly significant not only on the accuracy of results, but on their interpretation and application beyond the laboratory.

Another study, organised by the Forensic Science Service of Great Britain (as cited in Rowe, 2001), compared the confidence and accuracy of results submitted by 4 different laboratories, in which they scored 98, 60, 46, and 43% respectively. This study found that the standard of training which hair examiners are exposed to significantly

impacts their level of performance, with the laboratory scoring 98% utilising intensive training delivered by experienced hair examiners and the other laboratories undertaking sporadic or underwhelming training (Rowe, 2001). Additionally, as there are no accepted standards regarding the number of characteristics required to determine a microscopically similar ‘match’ (NAS, 2009; Taupin, 2004), quality and consistent training is paramount to the standardisation of microscopic hair analysis.

An additional major limitation of microscopic hair analysis is that an individual’s hair morphology is not uniform; meaning that even hairs originating from the same person and body location, may vary in their features (Giannelli, 2010; Taupin, 2004). Smith and Linch (1999) also highlight that many characteristics of a person’s hair may also change over time through both natural and unnatural treatment such as greying with age or colouring with chemicals respectively. Further, as the prevalence of any specific feature or internal characteristic, known as a ‘microtype’, in any given population is currently unknown, no statistical determination that a hair originated from any specific individual over another can be made (Smith & Linch, 1999).

One study of hair proteins in samples of different ethnicities and body sites by Laatsch et al. (2014), suggested that the value of hair evidence may be enhanced when it is subjected to microscopic examination, DNA analysis and proteomic characterisation, as this may assist in establishing the body site origin of the hair. This study also

expressed that the development of a searchable database may be possible following extensive further research of hair structures and proteins to develop a statistical classification scheme (Laatsch et al., 2014).

Given that the reliability of microscopic hair comparisons is indicated to be directly related to examiner training (Rowe, 2001); to best reduce future wrongful convictions related to microscopic hair analysis expert testimony, the industry must focus on education and training. Excellent training and experience are essential to producing quality examiners; as qualities are propagated through ‘generations’ of examiners, levels of skill, standard and confidence are passed from one ‘expert’ to the next (Cole & Duster, 2016). This works both positively and negatively, and therefore it is imperative that relevant standards are upheld to the highest degree to ensure competence. Such educational improvements should also be extended to the non-scientific community, so as to increase the understanding of the technique and the scope of its application in the criminal justice system.

As microscopic hair analysis remains highly accessible and useful in criminal cases today, further research is highly suggested to develop the literature on microscopic hair analysis error-rates and reliability. Further, expanding research to the identification of common microtypes observed in different populations beyond a Caucasian focus, may lead to significant developments in classifications and error rates (Smith & Linch, 1999).

The development of an international database of hair characteristics and standards of education and training for hair analysts would also be beneficial. Examiners should also continue to suggest and investigate any other possible sources of a questioned hair, even after a positive microscopic characteristic match has been determined (Smith & Linch, 1999). This will ensure that the most comprehensive results are presented, and these should not significantly alter an investigative path.

In conclusion, the value of microscopic hair analysis as expert evidence has varied with the quality and type of testimony, however, it has stood the test of time well. Provided that it is not applied beyond its scope and is supported by comprehensive and high-quality training of examiners, microscopic hair analysis remains relevant to criminal investigation and prosecution despite criticisms and advancements in DNA analysis. The use of this non-destructive and highly informative technique will continue to prove valuable. The reliance upon individual’s training and subjective assessment to determine critical details from hair evidence is significant. With the introduction of non-human assistance in comparisons which otherwise cannot be distinguished, may prove valuable and routine in future....